Automatic diaphragm control



Fwszlz XR 2,453,693 D HEECWENDL :Mwlmn AUTOMATIC DIAPHRAGM CONTROL FiledSept. 5, 1946 i YMO ftse'/ Mdef 2.2. ana( {Mge/s `zl N697' needle 17auge fer fava/Hilfen of yaff /0' of horizontal rays of Patented Nov. 16,1948 UNITED -STATES PATENT OFFICE sky, New York,

and Lionel S. Hetherington, Rockville Centre, N. Y

Application September 3, 1946, Serial No. 694,444

4 Claims.

(Granted under the act amended April 30 The invention described hereinmay be manufactured and used by or for the Government for governmentalpurposes without the payment to us .of any royalty thereon.

This invention relates to a new and improved automatic diaphragm controlfor gun cameras and the like.

In using gun cameras on airplanes because of the varying lightconditions that must be met in Aaerial photography, it is very diiiicultand often impossible for ground crew members to predict the lightconditions under which the camera .will be required to operate and tomake the correct aperture setting for that condition.

It is an object of this invention to provide a -devcefor automaticallysetting a camera aperture in accordance with the reflected light towhich a photoelectric cell .Within the camera is exposed.

Another object of .the invention is to provide -anautomatic diaphragmcontrol that is of simple construction, sturdy, yet light andinexpensive to manufacture and which can be attached directly to thepresent gun camera now in common .use with slight modiiication and canbe attached to almost any other camera with va similar modication.

Other and further objects and advantages of .the present invention willbe apparent to those skilled in the art from a consideration of .thefollowing description of a specic embodiment of the invention shown inthe accompanying drawings wherein:

Fig. 1 is .an elevational frontal view partly in section.

Fig. 2 is an elevational sectional side view taken on the line 2`2 ofFig. 1, and

Fig. 3 isa .diagrammatic illustration of the complete electrical system.

Referring more specifically to the' drawing, numeral I designates ahousing that may be mounted in or from a part of the conventional cameracasing. 'Within the housing I is a rotatable light polarizing disc 2made of any suitable polarizing material having lthe gear faced ring 3circumscribed thereon and the retainer ring 4 holding said rotatablepolarizing disc 2 in position. Immediately adjacent said rotatablepolarizing disc 2 is a xed polarizing disc 5 mounted in the forward endof a light baille 6. Said polarizling discs are constructed to permitfree passage light through said discs whenv the planes oi said discs arein alignment. Upon rotation ,nisaid discs relative to each other,

of March 3, 1883, as

the passage of .light will be gradually blocked until it is entirelyrestricted from passing through said discs. The .light baille 6 directsincident light to thephotoelectric cell 'I of conventional construction..Any suitable photoelectric cell may be employed. In the constructionshown, a self generating Iphotoelectric cell 1, su-ch as the Westoncellis illustrated, which is capable of generating an electric currenthaving a Voltage pro- 10 portional to the intensity of the incidentlight.

The .output leads from .the cell are directly attached to the movingcoil of the sensitive magne-tic contact relay meter 8 of conventionalconstruction well known in the art as illustrated iny theLetters Patentgranted to R. K. Stout, No. 2,331,354, dated October l2, 1943, onVariable speed motor control. Said magnetic contact relay meter 8 has aneedle I'Iy pivotally mounted on a shaft actuated by the moving coil ofthe meter 20 and Ahas magnetic contacts I8, I8 mounted on either side ofthe needle I'I which form electrical contacts 4for lcompleting anthrough .the needle. The said meter has the reset .ngers 2l, 2Ivnormally biased by springs (not shown) out of engagement with theneedle Il and actuated by an electromagnet 22 for movingsaid needle outof contact with either of said .magnetic contacts .I8, i8 back toneutral position. Said meter 8 selectively controls the reversibleelectric motor B which, when energized, rotates the shaft I0, said shafthaving the worm I I which meshes with and actuates the gear toothedperiphery of ring 3 to rotate the polarizing disc r2. Said shaft In alsohas the worm I2 which '3 meshes with the gear toothed periphery of ringI3 which is adapted to actuate the conventional iris diaphragm I4controlling the aperture of a camera lens. Mounted on the shaft I0 isthe 40 cam l5 Vadapted to actuate an electrical switch 'I6 to energizethe electromagnet 22 once during each revolution of the shaft I0. Asuitable battery v25 supplies .current for operation of the .motor 9 andfor energizing the resetting electro- 445 .magnet 22. Any suitable geartrain and driving mechanism maybe employed to accomplish thesimultaneous movement of the disc 2 and iris diaphragm M.

In use, .a suitable voltage is chosen on the low A`50 .side ofthephotoelectric cell I by xing a light .median .such as foot vcandles tomaintain the needle of the meter 8 in neutral position and the,rotatablepolarizing disc 2 is adjusted to that posi- `tion. .Asincident-lightenters through the polar- .55 .izingniscstz-nnd andcis.directed by the baille UU-HU.:-

Ii to the photoelectric cell 1, a constant voltage will be maintainedthrough the meter which will maintain the needle I1 in neutral positionas long as a light intensity of the selected value, such as 50 footcandles, is maintained. Increasing or decreasing changes in lightintensity of 5 foot candles impinging on the photoelectric cell I willvary the voltage output of the photoelectric cell sufficient to causethe needle I1 of the meter 8 to swing to one side and be maintained inmagnetic contact with the appropriate magnetic contact I8, closing thecircuit to the motor 9, energizing said motor and causing the shaft I6to rotate, which rotation imparts movement through the worm I I to therotatable polarizing disc 2 and which imparts movement through the worml2 to the iris diaphragm I4. Rotation of the disc 2 relative to the disc5, moves the polarizing axes of the discs further into or out ofalignment, increasing or decreasing the light barrier. In the event thelight passing through the discs 2 and 5 is oi greater intensity than thepreselected median, the photoelectric cell will develop an increasedvoltage, which will ultimately be sufficient to cause the needle I1 ofthe sensitive relay 8 to deflect from neutral position and moving sameto one side where, by magnetic attraction, it is drawn and held incontact with the magnetic contact I8, completing the circuit from thebattery 25 through the contact I8 to the motor 9, energizing said motor9, which drives the shaft ID and imparts rotation to the rotatablepolarizing disc 2 and iris diaphragm I4. This rotation of the polarizingdisc 2 will move the polarizing axes of the discs 2 and 5 further out ofalignment and will decrease the amount of light passing through saiddiscs 2 and 5 to the photoelectric cell 1. In the event the lightstriking the photoelectric cell is of less intensity than thepreselected median, the output voltage of the photoelectric cell will bedecreasedso that the needle I1 will move to the opposite side and willbe drawn into contact with the opposite magnetic contact I8, closing thecircuit through the contact I8 to the motor 9, energizing said motor inreverse, causing the shaft I to be rotated in reverse direction androtating said disc 2 in the reverse direction to bring the polarizingaxes of the discs 2 and in closer alignment, permitting a greaterintensity of light to pass through said discs to the photoelectrio cell1 and simultaneously increasing the aperture opening of the irisdiaphragm I4. Upon completion of one revolution of the shaft Il), thecam I5 will make contact with the switch contact I6 completing thecircuit through said connection to the electromagnet 22 which, throughmagnetic action on the lower ends of the ngers 2D. moves the needle I1back to neutral position breaking the contact and de-energizing themotor 9. This action will be repeated until the rotatable polarizingdisc 2 has been moved to a position where the incident light passingthrough the polarizing discs 2 and 5 to the photoelectric cell 1 hasbeen reduced or increased to the preselected intensity and the voltageoutput of the cell returned to a value corresponding to the neutralposition of the needle I1 and the aperture of the camera thus adjustedto the desired position.

Having thus described our invention what we claim is new and desire tosecure by Letters Patent oi the United States is:

1. In a control for automatically varying the light aperture of acamera, the combination of a rotatable iris diaphragm forcontrollingflight I YI admission to the camera, a photoelectric cell, arotatable polarizing diaphragm and a nonrotatable polarizing diaphragmfor controlling light admission to the photoelectric cell, a double neldcoil reversible electric motor, an electrical current source, arotatable power shaft connecting said motor to said iris diaphragm andsaid rotatable polarizing diaphragm to rotate them in unison, an ammeterelectrically connected to the output circuit of said photoelectric celland adapted to assume a medial position at a preselected output of saidphotoelectric cell, a double throw switch adapted by actuation of saidammeter above or below said medial position to direct current to one orthe other of said iield coils, an electromagnet, a cam operated controlswitch closable by each rotation of said power shaft to periodicallyenergize said electromagnet, and linkage movable by energization of saidelectromagnet to intermittently reset said ammeter to its medialposition.

2. In a control for automatically varying the light aperture of acamera. the combination Aoi a rotatable diaphragm for controlling lightadmission to the camera, a photoelectric cell, a second rotatablediaphragm for controlling light admission to the photoelectric cell, anelectric motor. selective means to rotate said motor in eitherdirection, an electrical current source, a rotatable power shaftconnecting said motor to said diaphragms to rotate them in unison, anammeter electrically connected to the output circuit of saidphotoelectric cell and adapted to assume a medial position at apreselected output of said photoelectric cell, a double throw switchadapted by actuation of said ammeter above or below said medial positionto operate said `selective means, an electromagnet, a control switchclosable at each turn of said power shaft to momentarily energize saidelectromagnet, and linkage movable by energization of said electromagnetto intermittently reset said ammeter to its medial position.

3. In a control for automatically varying the light aperture of acamera, the combination of a rotatable means for controlling lightadmission to the camera, a photoelectric cell. a second rotatable meansfor controlling light admission to the Aphotoelectric cell, an electricmotor, a reversing means for said motor, an electrical current source, apower transmitting means connecting said motor to said rotatable meansto rotate them is unson, an ammeter electrically connected to the outputcircuit of said photoelectric cell and adapted to assume a medialposition at a preselected output of said photoelectric cell, a doublethrow switch adapted by actuation of said ammeter above or below saidmedial position to operate said motor reversing means, an electromagnet,a control switch closable by operation of said power transmitting meansto periodically energize said electromagnet, and linkage movable byenergization of said electromagnet to intermittently reset said ammeterto its medial position.

ing lsaid power source .to said poweractuated means to rotate ltheminvnison, an ammeter CHARLES W. ARMSTRONG. CHARLES SADOWSKY. LICNEL S.HETHERINGTON.

6 REFERENCES CITED The following references are of record in the le ofthis patent:

Number 10 Number UNITED STATES PATENTS Name Date Bartels Feb. 7, 1939FOREIGN PATENTS Country Date France Feb. 12, 1934 France Aug. 17, 1937Germany Aug. 19, 1937 Great Britain Sept. l, 1938

